Voice coil actuators are used in many systems, such as magnetic and optical disc drives. The voice coil actuators are using with open or closed-loop tracking systems. Close loop systems such as with optical data drives and hard discs use data read from the surface of the disc as feedback within the closed loop to ensure position or make necessary corrections. Open loop tracking systems using voice coil actuators such as in floppy drives or optical labeling drives must ‘dead-reckon’ and have significant sensitivity to shock and vibration.
Most actuators use only their spring tethering to maintain their position in the presence of shock and vibration. In optical drives, such as CD audio players, large buffers of data are used to continue to play music during shock events until the tracking system can recover. In drives that write data, such shock and vibration causes a significant displacement of the actuator that may show up as corrupted data when later read or as visual artifacts if one uses the actuator to label a surface. Therefore, there is a need for a control system that is able to minimize motion of the actuator in the presence of shocks and vibrations.